Bash script sed usage causing issues in ZSH

I have a Bash script that I use to pull in several repos to create a new instance of our project workflow, which carries out a number of string replacements based on information provided from the command line.

A colleague uses ZSH and has been experiencing issues that seem to be as a result of the use of

sed

in the script. Specifically it seems to be that it's not processing the regex? For example...